Anemometer



Nov. 20, 1962 DE HEER E.TAL

ANEMOMETER 2 Sheets-Sheet 1 Filed Feb. 4, 1960 United States Patent 3,064,473 ANEMOMETER Tallechienus de Heer and Paul Johannes Erkelens, The

Hague, Netherlands, assigners te Nederlandse rganisatie voor Tegepas-Natuurwetenschappelijk Underzeek ten behoeve van de Volksgezondheid, The Hague Netherlands Filed Feb. 4, 1960, Ser. No. 6,781 Claims prierity, appiicatien Netherlands Feb. 17, 1959 2 Claims. (Cl. 73189) The determination of the direction of a slow air moten in a space is eiected by means of pennants, threads and the like, which are held in the air on rods. Frorn such rneans certan deductions can be made, but it is only exceptionally that this determinaon yields data which are fit for calculating purposes, while no information is given abent the velocity, uniess some ether more comprehensve mechanism is used, which, however, is apt to have a disturbing eiect.

An anemorneter is disclosed in U. S. Patent No. 2849,880, which -anernometer is provided with a heated ferk placed en a base and a thennoelement. With this anemometer the velocity can be calculated from the temperature. It must, however, first be arranged in the right direction relative to the air stream.

The present invention relates te an anemometer for determining the direction as well as the velocity of a slow gas or air motion.

According to the invention ths anernemeter is provided with a fork, the heated legs of which are perpendicular te each ether, and with two feelers having a thermoelement each, which feelers are parallel to the fork legs, and is also provided with a driving gear, which causes the ferk legs te carry out a retation about the feelers, and with a registering apparaus for the position of the fork legs with respect te the feelers as well as for the temperature of the therrnoelernents.

The fork legs, which are heated te equal temperatures, prodnce a wake flow in the air stream te be measured, the temperature of which wake flow differs frorn that of the air stream itself due to convecton.

This wake flow naturally follows the movement of the fork legs and where said legs carry out a rotation about the feelers a change in the temperature of the thermoelements is brought abont, which results in a temperatnre curve which depends en the positien of the leg with respect to feeler. This curve indicates with precision when the wake flow reaches the feeler and leaves it free again, trom which the sze of the wake flow can be derived, and frorn this sze, according to forrnniae known in the art, the air velocity can be deterrnined.

Becanse the two 1egs and also the feelers are perpendicular te each other, the direction may be determined in very simple fashon from the two graphs of the temperatures with respect to the position.

Becanse in the anemerneter according te the invention the heated legs -are used as the disturbance profile, and because only temperature dfierences deriving trom said legs are measured, a much greater freedom for using the anemorneter according to the inventien for air motions having different and frequently high temperatures has been created.

The invention is hereinafter further described with reference to a drawing in which some ernbodiments of an anemorneter accordng to the invention and also some of its details and a temperature curve which was registered are schematically shown.

FIG. l shows a perspective arrangement of the fork legs, the feelers and the supporting and driving mechansms.

FG. 2 shows a longitudinal cross-sectien through a driving gear.

FIG. 3 shows a diagram of the wake flow in diflerent positions.

FIG. 4 shows a graph showing the connection between temperatnre and angle positon.

FIG. 5 shows the correlation between the angles p which have been measured and the angles with a fixed system of co-ordinates with respect to the anemometer.

A case 1 is provided with a mounting element 2, by means of which the meter can be mounted on a pedestal er seme ether device in a space in which the air motion which is te be examined eccurs.

On the case is a fixed yoke 3 in the corner points of which are mounted two feelers 4 and 5 directed towards each ether while being at right angles te one another. Betl1 feelers are equipped with temperature sensng elernents, the leads 6 of which lead through the yoke 3 te a registering apparatus R, such as a conventional continuous recording micro-arnmeter-rnicro-voltmeter which records en a mtwing chart the temperatures sensed. The registering apparatus R is connected to the leads 6 of the feelers, and in order to correlate the recorded temperature with the position of the fork legs with respect te the feelers, there is a connection provided between the registerng apparatus and the driving means 10 and the carrier 7 for the fork legs. This connection, shown as a line in FIG. 1, can be any type of connection which insnres that the registering apparatus is dn'ven at a speed proportional te the speed of rotation of the fork legs, e.g. a synchronous motor eennection or a direct drive connectien.

In the bisector plane of the feelers 4 and 5 a carrier 7 having two fork legs 8 and 9 is moved by a mechanisrn mounted in the case 1, which mechanism is driven by an electrornotor 19 having leads 11, the motor being accommodated in the case.

The fork legs 8 and 9, the same as the feelers 4 and 5, are at right angles to one another and by the movement of the carrier 7 they describe a cylinder around the feelers of elliptic cross-section.

The fork legs are heated electrically With the aid of built-in heatng elements which are fed throngh leads 12. As a matter of course the same energy is supplied te both legs.

The moton of the carrier 7 is obtained with the aid of the mechanism according te FIG. 2.

The carrier 7 is cennected to a ring 13, in which a disc 15 can rotate, said disc being fixed eccentrically with respect te a shaft 14 which can rotate in the case 1. At the opposite end of the ring 13 an extension piece 16 of the carrier 7 is provided.

The carrier 7 and the extension piece 16 are slidably mounted in a second ring 17. This ring 17 can only carry ont a horizontal rnovement in the case 1, because pins 18 of the ring 1'7 can slide backwards and forwards in slots 19 in the case 1.

The shaft 14 is driven by the motor 10 and in this manner each point of the carrier 7 follows a circular path as is indicated by point 20. The angle 1! is used as the abscissa for the graphs, and the line n, which is perpendicular to the plane through the feelers is taken as the 0, the temperature being the ordinate for said graphs.

The legs 8 and 9 each enclose an angie of 45 with the plane in which the carrier 7 moves, but naturally follow the movernent of said carrier, whereby, therefore, they do not describe a trne crcular cylinder, bilt an elliptical cylinder, the long axis of which is horizontal and is larger by /2 than the short axis, as shown in FIG. 3 in a sectional view of a feeler 5 and a leg 9.

An air motien from a direction as ndicated by the arrow 21 and having a given velocity, in brushing past a fork leg 9 wil1 produce a particular wake flow 22,

which wake flow will attain a temperature which diters from .the temperature .of.the air and which is causecl by conduction from the heated fork legs, which wake flow moves along with the leg 9.

As soon as the wake flow 22 in the position 9a of the leg 9 at an angle hits the feeler 5, which causes the latter to be heated, the temperature of said feeler rises and agraph such as is represented in FIG. 4 of such temperature for various angular positions can be drawn, and in which graphs it is seen that with the legs in the 9m position the maximum temperature is reached;while in the 92 position the temperature has dropped again, because the wake flow 22 has passed the feeler.

Because the angular position p of the fork legs has been set out horizontally and the temperature of the two thermoelements in the feelers vertically, it is possible in a simple way to derive from the curves I and 11, from which direction With respect to each of the feelers the air motion comes.

Because the legs as wellas the feelers are at right angles to each other, deterrnining the direction in the space is possible.

FIG. 5 illustrates the relationship existing between the measured angles -J/ and b of the peaks in two curves and belonging together, and between the angles al and ad of the direction of velociy 21 With a system of coordinates fixedrelativete tl1e anemometer.

T'ne system of co-ordinates is formed between the plane V through the legs 8 and 9, and the plane N in which the motion takes place, i.e. the plane in which the cross-secti0n 0fFIG. 2 has been taken, and the horzontal plane H.

'he direction 21 of the veloeity of the air together with the legs 8 and 9 forms two planes ADE and BFG,

in which the maximum temperature is measured. Said planes intersect the plane N en lines which form angles p and with the normal n to the plane V.

If the angles and 31 n are known from the graphs the angles al and ad which are formed by the direction 21 with the system of co-ordinates, can be determined by the aid of stereometry either from the figure or from a goniometric connection.

As a matter of course ether driving mechanisms for the fork legs are also possible, provided they both carry out equal movernents wth respect to the feelers.

In addition to the direction 21 of the velocity, the magnitude of the velocty can be derived fr0m the width of the temperature curve halfway to the top. (Grenzschinhttheorie, a book by H. Schlichting, 1951 Edition page 447-449.)

We claim:

1. A11 anemometer for .measuring the direction and velocity of a current of gaseous medium, comprising a fork member having at least two legs at an angle to each ether, means for heating said legs, a carrier on which said fork member is mounted, a plurality of fixedtemperature sensing feelers, one positioned parallel to each leg of said fork member, a driving means on which said carrier is mounted driving said fc rk member and said legs around said feelers with the feelers and legs substantally parallel to each other during the rnovement of the legs relative to the feelers, and means coplecl to said driving means and carrier for indicating -the dfierent positions of the fork legs with respect to said feelers, whereby when the temperatures sensed by said feelers at the difr'erent positions of said legs relative to said feelers are plotted against the angular positions of said legs relative tosaid feelers, the velocity of a gaseeus medium passing said legs and feelers as well as the direction of movement 'of said gaseous medium can be calculated.

2. An anemorneter as claimed in claim 1 in which there are two fork legs and two feelers, said legs being at an angle of te each other and said feelers being at an angle of 90 to each other.

References Citetl in the file of .this patent UNITED STATES PATENTS 2,849880 Obermaier Sept. 2, 1958 

